Plumes of steam escaped mugs on the table, filling the room with the rich scent of coffee. Rose's house was small and cluttered with blankets strewn across the couch and picture frames adorning every wall. The sound of the children playing upstairs echoed down the hall, their excited footsteps thudding against the living room ceiling.

Margaux took a sip of her coffee as her friend waited anxiously for her to continue speaking.

"And…?"

"And…" She sighed. "He didn't say it back."

Rose grimaced, visibly cringing.

"Yeah..." she nodded.

"Oh, I'm sorry Marg." Rose shuffled closer on the couch and patted her arm.

"It's okay. Like really, I'm fine. It's Sherlock Holmes, I don't know what I was bloody expecting him to say."

"Yeah, you're right. I mean, it's not like you haven't spent the last three years raising his son."

"Ah well see, unfortunately, sharing a child with someone doesn't entitle you to their love."

"Tell that to my ex."

Margaux laughed into her cup.

Rose tilted her head, she knew her friend too well. "So how long are you going to keep saying you're fine before you admit you're absolutely not fine?"

"About a week?"

Vaughan toddled into the living room. He walked up to his mother and patted her on the leg. "Mummy, can we go now?"

Margaux sighed through a smile. "Sure. Come on then." She stood up and put on her coat.

"Where are you off?" asked Rose.

"Taking Vaughan to see father dearest."

"I'm going to see my Daddy!" the boy sang with an excited grin. "He's been sick but he's better now."

Rose watched as Margaux zipped up his coat and pushed a woollen hat onto his head. "How's John Watson doing?" she asked.

"You know you don't have to full-name him every time?"

"Sorry. I read his blog, it's a bad habit."

"You read his blog?"

"Yeah! Did you know they almost got killed once by the Chinese circus?"

III

John Watson sat in the usual cream, leather chair; his legs were crossed in front of him as they usually were, his therapist's head tilted slightly to one side as it usually was. He was feeling better, almost proud to show her his improvement as he spoke about how amazing his daughter was, how much better Sherlock was doing.

"What about his brother?" asked the therapist in her soft German accent.

"Mycroft? He's fine," replied John. "I mean, obviously 'normal' and 'fine' are both relative terms when it comes to Sherlock and Mycroft."

She smiled. "Obviously." She paused for a moment, still smiling. "I didn't mean Mycroft. I meant the other one."

"Wh-which other one?"

"You know, the secret one."

"Oh, that was just something I…" he smiled, almost laughing. "I said. I'm sure there's…" He stopped. His eyes narrowing as he looked across to her. "How did you know about that? I didn't tell you that."

"You must have done," she replied flippantly.

"I really didn't."

"Well, maybe Sherlock told me."

John shifted forward in his seat. "No. You've met Sherlock exactly once. In this room. He was off his head."

"Oh, no, no. I met him before that."

"When?"

"We spent a night together." She smiled at the memory. "It was lovely. We had chips."

He blinked rapidly, his heart pounding as the therapist's German accent began to morph into another.

"You're not what I expected, Mr Holmes." She exaggerated each word. "You're… nicer." She took off her glasses. "Culverton gave me Faith's original note. A mutual friend put us in touch." She walked across the room to the glass patio doors, locking them and removing the key. "Did Sherlock ever tell you about the note? I added some deductions for Sherlock. He was quite good. But… He didn't get the big one."

John watched in bewilderment as the woman reached her fingers into her eye and popped out a brown contact lens. He glared at her face, at the stark contrast of blue and brown, the plastic daisy tucked behind her ear.

"What's that?" He asked.

"What's what?"

"The flower in your hair. It's like I had on the bus…"

"You looked very sweet. But then…" she bent down to look at him. "You have such nice eyes."

John collapsed back into his chair. The woman on the bus. E.

"Amazing the times a man doesn't really look at your face. Oh, you can hide behind a sexy smile, or a walking cane, or just be a therapist, talking about you all the time."

He stood up quickly. Yet as suddenly as he rose from his chair, the woman had pointed a gun at him. He raised his hands, backing away.

"Oh, please don't go anywhere. I'm sure the therapist who actually lives here wouldn't want blood on the carpet. Oh, hang on, it's fine. She's in a sack in the airing cupboard."

"Who are you?"

"Isn't it obvious? Haven't you guessed?" she said, almost offended. "I'm Eurus."

"Eurus?"

"Silly name, isn't it? Greek. Means the East Wind. My parents loved silly names, like Eurus… or Mycroft… or Sherlock."

John's eyes widened, his mouth dropping slightly as he stared at her.

"Oh, look at him. Didn't it ever occur to you, not even once, that Sherlock's secret brother might just be Sherlock's secret sister?"

He couldn't compute it. John often felt stupid in the presence of a Holmes, but never lost for words. He frowned, his mind desperately trying to connect it all together – to make sense of it.

"Huh," said Eurus. "He's making a funny face. I think I'll put a hole in it." She pulled the trigger.

John hunched over with his arms shielding his head. He waited for the impact – the pain. But it never came. After a few moments he glanced up, his breath shallow as he laid eyes on Eurus. She was standing with a smile on her face, the gun outstretched as smoke billowed from the barrel. He glanced behind him, looking for a bullet hole, when suddenly, he began to feel woozy. He looked down at his arm. A tranquiliser? She… He looked up again, his knees buckling beneath him, his eyes beginning to close.

"Tell Sherlock I look forward to seeing him again," said Eurus.

III

Sherlock stood in the kitchen with a hand on his hip as he waited for the kettle to boil. On the counter beside his teacup was the yellowed note from his night with Culverton's daughter – the night he thought he had imagined. He shook his head and slid the note into his pocket as the sound of footsteps clattered up the stairs.

"Daddy?"

"In here." He turned around, his cold, alabaster face warming with a smile as he laid eyes on his son.

"Daddy!" Vaughan ran to him, clinging to his leg and hugging him tight.

"I still don't know why you're so fond of me," said Sherlock as he picked him up.

"Neither do I," Margaux added as she stepped around the corner into the kitchen.

They stood quietly, looking at each other. He always hated when John said he could cut tension with a knife. But in this moment, it was as if the tension truly was tangible – like a thick fog hanging above their heads.

"I've brought some toys," said Margaux, gesturing to the little green backpack in her hand. "So he can play with those instead of the jar of eyeballs like last time."

"I don't see what the problem was. He didn't open the jar."

"Maybe let's just stick to building blocks and dolls instead of human remains, okay?"

"Fine. But if he's disappointed I'm blaming you." He put Vaughan down and watched as he walked into the living room and picked up his little violin.

Sherlock and Margaux stayed in the kitchen. An awkward silence joined the tension in the air as they stood looking at each other. He watched as she pushed her hands into her pockets, shuffling on her feet.

"So…" he said.

"Yeah." She cleared her throat. "Well, I'll come and pick him up later. Have fun."

She turned her back on him and walked towards the door.

"Maybe…" Sherlock blurted out.

She turned around.

"Maybe you could… stay?"

"Oh."

"Unless, of course, you have somewhere to be. I don't– I just thought…."

"Oh. S-sure, yeah, I can stay." she nodded.

"Good."

His eyes scanned her as they stood across from each other; she was chewing her lip, her cheeks flushing gently – she was uncomfortable. He opened his mouth to speak but nothing came out.

"Oh, this is ridiculous." Margaux rubbed her forehead. "We shouldn't be acting like this over one little 'I love you'; we've seen each other naked, yet this is what we get weird over?"

"Why are you equating embarrassment to seeing me naked? Should I be embarrassed about something?" He gestured to his body.

"No! Of course not! I just… oh god." She stopped suddenly, her eyes narrowing. "Wait, hang on, I never said I was embarrassed. It's you who just made that connection, not me. Oh god, should I be embarrassed!?"

"Of course not! Your body is perfectly… operational."

"Perfectly operational!?" she scoffed in astonishment.

"Yes? I… do things and it responds accordingly. That's a compliment, isn't it?"

"No, Sherlock. You pretty much just referred to me as a sex doll with lungs." She covered her face in despair before throwing her head back. "Oh god, we've just made this ten times worse than it already was." She approached him swiftly, placing a hand on his arm. "Listen, I'm not embarrassed about what I said. Because I meant it. I don't feel embarrassed, so you shouldn't feel awkward. Okay?"

He nodded.

"Come sit down. By the sound of it, your son could really do with some more violin lessons."

They walked into the living room, taking their seats in the armchairs by the fire.

"Sherlock!?" John's voice bellowed from the staircase. "Sherlock, are you up there!?" He hurried through the door, panting heavily as he stopped in the middle of the living room. "Sherlock…"

"Yes?"

"I… I don't quite know how to tell you this..."

Sherlock scanned his friend, from the flyaway hairs on the top of his head to the scuffs on his shoes. "With words, would probably be the most effective way," he said.

"I just met your sister."

Margaux's brows came together. She glanced over to Sherlock who remained calm in his chair.

"Mm no you didn't, I don't have a sister," he replied bluntly.

"No, Sherlock, you do."

"A whole human being is something I think I'd remember…"

"Eurus. She said her name was Eurus. It's Greek for–"

"The East Wind." Sherlock dropped his gaze for a moment, shaking away memories of his childhood that began to creep in.

"Sherlock, she was the woman you had chips with. You didn't imagine it! It was her, pretending to be Culverton Smith's daughter." John pulled up a chair and sat down. "She's been posing as my therapist, and she's the one I was texting before Mary died."

"You were texting another woman?" Margaux interjected.

"Not now, thank you, Margaux," John said with a passive-aggressive smile. "She's been hiding all over the place – wearing disguises to get close to you. She had contact lenses in, Sherlock. Brown ones. You know why? Because her real eyes are bright bloody blue, just like yours."

"It's preposterous," Sherlock scoffed.

"I think I've met her too," said Margaux, her back straightening. "There was a woman in the hospital when Mary was having Rosie. She sat next to me and we talked; she steered me into talking about Sherlock. I thought she looked familiar, I swear that wasn't the first time she's made contact with me."

"You both sound ridiculous, and that's coming from me. How could my parents fail to mention they had a daughter?"

"Mycroft." Said John. "Mycroft knows everything."

"Y'know, Mycroft said something to me once, over a year ago now," said Margaux. "I found it odd at the time but I assumed he'd just misspoken. He said: 'I learned a long time ago to stop analysing my siblings.' Siblings. Plural."

"Yes, Margaux, though the English language can be difficult, I'm sure we're all aware that 'siblings' means more than one." Sherlock rolled his eyes and stood up.

"He said something like that to me too," said John, pulling his chair closer to Margaux. "He said: 'It didn't the last time and it wouldn't with Sherlock'."

Sherlock turned his head sharply. "What didn't the last time? Were you talking to Mycroft about me?"

"That's not important right now."

Sherlock sighed, his jaw clenched, his entire body tensing as he stood with his arms behind his back. "John, I decipher facts from miniscule observations that the average person wouldn't even see if you pointed it out to them. I'm Sherlock Holmes, a sister is something I'm pretty sure I'd remember."

"Okay, Sherlock Holmes," he replied, mocking his voice. "Well Eurus Holmes just introduced herself by shooting me with a tranquiliser and knocking me out for two hours. He stood up and walked over to him. "She's dangerous. And she seems to think you'll be meeting her soon."

Vaughan shook his head and sighed. "Mycof is naughty."

The three adults looked at one another with wide eyes.

"Well clearly someone got his observation skills from his father," said John.

III

"You have to sit in the chair," said Mrs Hudson. "They won't talk to you unless you sit in the chair. It's the rules."

"I'm not a client," Mycroft spat.

"Then get out," said Sherlock, his voice smooth like honey.

Mycroft glared down at the two men as they sat in their armchairs. While Sherlock sat with one leg over the other, his palms together beneath his chin, John twiddled a pen between his fingers, a smirk fighting with the corners of his mouth.

He sat down reluctantly, still angry with them for frightening him in his home the night before. He shuddered, before turning his attention to Mrs Hudson as she stood in the doorway.

"She's not going to stay there, is she?"

"Would you like a cup of tea?" she asked sweetly.

"Thank you."

She pointed to the kitchen. "The kettle's over there."

Sherlock and John exchanged a smile.

"So, what happens now?" said Mycroft. "Are you going to make deductions?"

"You're going to tell the truth, Mycroft, pure and simple," Sherlock replied.

"Who was it said: 'truth is rarely pure, and never simple'?"

"I don't know and I don't care. So, there were three of us. I know that now. You, me and… Eurus."

Mycroft nodded.

"A sister I can't remember," Sherlock continued. "Interesting name, Eurus. It's Greek, isn't it?"

"Mm. Yeah, er, literally 'the god of the East Wind'," said John.

"Yes."

"'The East Wind is coming, Sherlock'. You used that to scare me."

"No."

"You turned my sister into a ghost story."

"Of course I didn't. I monitored you."

John's brow furrowed. "You what?"

"Memories can resurface." Mycroft turned to him. "Wounds can reopen. The roads we walk have demons beneath. And yours." He turned to Sherlock. "Have been waiting for a very long time. I never bullied you. I used – at discrete intervals – potential trigger words to update myself as to your mental condition. I was looking after you."

"Why can't I remember her?" Sherlock's voice was dark; soft yet intense.

Mycroft looked at John. "This is a private matter."

"John stays."

"This is family."

"That's why he stays."

John couldn't help but smile slightly. He lowered his head, staying put in his chair. "So there were three Holmes kids," he finally said. "What was the age gap?"

"Seven years between myself and Sherlock; one year between Sherlock and Eurus."

"Middle child." He pointed his pen at Sherlock. "Explains a lot. So did she have it too?"

"Have what?"

"The deduction thing."

"'The deduction thing'?"

"Yes..."

"More than you can know."

"Enlighten me."

III

Fire engines and police cars littered the length of Baker Street. Margaux pulled up in her car and jumped out, looking up at a thick trail of black smoke rising towards the blue sky. She hurried towards the police tape that cordoned off the street.

"Sorry, miss, there's been an incident. No access down this road at the minute," said a police officer, holding his arm out to stop her ducking under the tape.

"Oh, er..." She reached her hand down the front of her coat and pulled out her police badge.

He nodded, apologising as he lifted the tape for her.

She ran down the street, her jaw hanging in shock as she approached the house. Smoke escaped through the holes that were once the windows of 221B. The wall had been scorched black and shattered glass and debris covered the ground below. An explosion, she thought, surely not. But when she saw Mycroft dealing with the fire and police services, she knew it wasn't such a strange thought.

Sherlock and John were gathered around the back of an ambulance, their faces and hands scuffed, blankets draped over their shoulders.

"What the hell happened!?" She shouted as she approached them.

"The East Wind," said John.

"What?"

"Jumped out the windows as the flat blew up," said Sherlock calmly. "Which reminds me, Mrs Hudson will need a place to stay until it's declared safe again."

Margaux glanced into the ambulance where Mrs Hudson sat with a paramedic.

"Of course, yes, she can stay with me," she said. "But that doesn't explain what the bloody hell happened here!"

"John already told you… The East Wind."

She paused for a moment. "Eurus? Your sister did this?"

"Can we lower our voices?" said Mycroft as he stepped up behind her. "I'd rather you didn't announce her existence to the entire street."

Margaux looked up at the charred building and back to Mycroft as he towered above her. "Because almost getting blown up is really subtle," she replied sarcastically. "How are you explaining this one away?"

"Leaky gas pipe."

"Of course."

Mycroft took his phone out of his pocket and walked away.

Margaux turned back to the two men. "Why would she do this?"

"My brother's been hiding a lot," said Sherlock. "Seemingly because she's the most dangerous person on the planet."

"Seemingly," she nodded. "There's a hole in the side of Mrs Hudson's house."

"Mycroft has no idea how she's been escaping her secure facility," Sherlock continued, ignoring her quip. "So, we're going to find out." He looked over to Mycroft who was waving them over. "John and I are going on a business trip."

"More like a family reunion," said John.

"Shan't be long." He threw off his blanket, straightening his suit jacket and running his fingers through his hair.

Margaux grabbed him by the arm, turning him back around to face her.

"Be careful," she said.

"Always am." He winked, before hurrying to catch up with John and Mycroft. "Well, maybe not always," he shouted.